1,120 research outputs found
Comment on ``A New Symmetry for QED'' and ``Relativistically Covariant Symmetry in QED''
We show that recently found symmetries in QED are just non-local versions of
standard BRST symmetry.Comment: 4 pages, revte
Negative Link Prediction in Social Media
Signed network analysis has attracted increasing attention in recent years.
This is in part because research on signed network analysis suggests that
negative links have added value in the analytical process. A major impediment
in their effective use is that most social media sites do not enable users to
specify them explicitly. In other words, a gap exists between the importance of
negative links and their availability in real data sets. Therefore, it is
natural to explore whether one can predict negative links automatically from
the commonly available social network data. In this paper, we investigate the
novel problem of negative link prediction with only positive links and
content-centric interactions in social media. We make a number of important
observations about negative links, and propose a principled framework NeLP,
which can exploit positive links and content-centric interactions to predict
negative links. Our experimental results on real-world social networks
demonstrate that the proposed NeLP framework can accurately predict negative
links with positive links and content-centric interactions. Our detailed
experiments also illustrate the relative importance of various factors to the
effectiveness of the proposed framework
The Several Guises of the BRST Symmetry
We present several forms in which the BRST transformations of QCD in
covariant gauges can be cast. They can be non-local and even not manifestly
covariant. These transformations may be obtained in the path integral formalism
by non standard integrations in the ghost sector or by performing changes of
ghost variables which leave the action and the path integral measure invariant.
For different changes of ghost variables in the BRST and anti-BRST
transformations these two transformations no longer anticommute.Comment: 3 pages, revte
Compact non-invasive millimeter-wave glucose sensor
The authors describe a compact non-invasive CMOS-circuit-based glucose monitor using millimeter-wave transmission for use on animal and human subjects. Using an earlier device, in vivo measurements were performed through the ear in anesthetized animals and correlated with blood glucose concentration from test strips. In addition, millimeter wave absorption through glucose-containing solutions was measured in specialized liquid transmission cells and is shown to correlate with the animal and separate in vitro data. Design and performance information on the CMOS transceiver are given
Cooperative video transmission strategies via caching in small-cell networks
Small-cell network is a promising solution to the high video traffic. However, it has some fundamental problems, i.e., high backhaul cost, quality of experience (QoE) and interference. To address these issues, we propose a cooperative transmission strategy for video transmission in small-cell networks with caching. In the scheme, each video file is encoded into segments using a maximum distance separable rateless code. Then, a portion of each segment is cached at a certain small-cell base station (SBS), so that the SBSs can cooperatively transmit these segments to users without incurring high backhaul cost. When there is only one active user in the network, a greedy algorithm is utilized to deliver the video-file segment from the SBS with good channel state to the user watching videos in real time. This reduces video freezes and improves the QoE. When there exist several active users, interference will appear among them. To deal with interference, interference alignment (IA) is adopted. Based on the scheme for a single user, the greedy algorithm and IA are combined to transmit video-file segments to these users, and the performance of the system can be significantly improved. Simulation results are presented to show the effectiveness of the proposed scheme
White Matter Deficits Assessed by Diffusion Tensor Imaging and Cognitive Dysfunction in Psychostimulant Users With Comorbid Human Immunodeficiency Virus Infection
Background
Psychostimulant drug use is commonly associated with drug-related infection, including the human immunodeficiency virus (HIV). Both psychostimulant use and HIV infection are known to damage brain white matter and impair cognition. To date, no study has examined white matter integrity using magnetic resonance imaging (MRI) diffusion tensor imaging (DTI) in chronic psychostimulant users with comorbid HIV infection, and determined the relationship of white matter integrity to cognitive function.
Methods
Twenty-one subjects (mean age 37.5 ± 9.0 years) with a history of heavy psychostimulant use and HIV infection (8.7 ± 4.3 years) and 22 matched controls were scanned on a 3T MRI. Fractional anisotropy (FA) values were calculated with DTI software. Four regions of interest were manually segmented, including the genu of the corpus callosum, left and right anterior limbs of the internal capsule, and the anterior commissure. Subjects also completed a neurocognitive battery and questionnaires about physical and mental health.
Results
The psychostimulant using, HIV positive group displayed decreased white matter integrity, with significantly lower FA values for all white matter tracts (p < 0.05). This group also exhibited decreased cognitive performance on tasks that assessed cognitive set-shifting, fine motor speed and verbal memory. FA values for the white matter tracts correlated with cognitive performance on many of the neurocognitive tests.
Conclusions
White matter integrity was thus impaired in subjects with psychostimulant use and comorbid HIV infection, which predicted worsened cognitive performance on a range of tests. Further study on this medical comorbidity is required
Caching UAV-enabled small-cell networks
Unmanned aerial vehicles (UAVs) can be utilized to provide flexible wireless access in future wireless networks, with larger coverage and higher transmission rate. However, the wireless backhaul for UAVs is usually capacity-limited and congested, and UAVs cannot operate for a long time due to the limited battery life. In this paper, a framework of caching UAV-enabled small-cell networks is proposed, to offload data traffic for the small-cell base stations via caching. In the proposed scheme, the most popular contents are stored at the local caches of UAVs in advance, which can be delivered to mobile users directly from the caches when required. Thus, the congestion of wireless backhaul can be alleviated, the energy consumption can be reduced, and the quality of experience can be improved
Tricarbonyl(chlorodiphenylstannyl){η5-[2-(dimethylamino)ethyl]cyclopentadienyl}molybdenum
Reaction of the tricarbonyl{η5-[2-(dimethylamino)ethyl]cyclopentadienyl}molybdenum anion and dichloridodiphenylstannane affords the title compound, [MoSn(C6H5)2Cl(C9H14N)(CO)3], which exhibits a four-legged piano-stool geometry with chloridodiphenylstannyl ligands unperturbed by the pendant 2-(dimethylamino)ethyl groups. The Mo—Sn bond length [2.7584 (5) Å] and the distortion of the tetrahedral tin coordination geometry are similar to those observed in related tin-substituted tricarbonylmolybdenum and -tungsten complexes
Bimetallic metal-organic frameworks for controlled catalytic graphitization of nanoporous carbons
Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications
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